Water/Alcohol-Soluble Conjugated Polymers Based on Cyclopentadithiophene and Fluorene as Cathode Interlayers Elevate the Stability and Efficiency in Organic Solar Cells

In high-performance bulk heterojunction organic solar cells (BHJ OSCs), cathode interlayers (CILs) have been effective in enhancing the device stability and photovoltaic performance by reducing the electron traps of ZnO layers. In this work, three water/alcohol-soluble conjugated polyelectrolytes (CPEs), P2T-CDTNa, PC-CDTNa, and PNDIT-FNa, as cathode interlayers (CILs) are reported. The effect of these three CPEs is validated by using PBDB-T:ITIC and PM6:Y6 as photoactive blends. Compared with ZnO-only devices, all three ZnO/CPE-based devices demonstrate enhanced photovoltaic performances. Especially, the ZnO/P2T-CDTNa-based devices show impressive power conversion efficiencies (PCEs) of 9.93% (V-OC = 0.87 V, J(SC) = 16.56 mA/cm(2) , and FF = 69.04%) and 16.15% (V-OC = 0.84 V, J(SC) = 27.71 mA/cm(2) , and FF = 69.60%) for PBDB-T:ITIC and PM6:Y6 BHJ photoactive blends, respectively.

Automated summary

This study reports the use of three water/alcohol-soluble conjugated polyelectrolytes as cathode interlayers to improve the performance of high-performance bulk heterojunction organic solar cells. Compared with devices using pure ZnO layers, devices using these three polyelectrolytes demonstrate enhanced photovoltaic performance, with the device incorporating P2T-CDTNa showing the best results.